Jan 20, 2017

Seals Use Their Whiskers to Detect the Breathing of Hidden Prey

The whiskers on a harbor seal are more than just a touch of added cuteness - they're hunting tools that help it detect the smallest perturbations of water made by its favorite food hiding on the seafloor.

That's what researchers from the University of Rostock (UR) found when they tested the animals for the ability, in research just published in the Journal of Experimental Biology.

The prey at the root of the experiment, flatfish, a favorite food of harbor seals, are camouflage experts that can hide in plain sight or burrow under the sand on the seafloor. Trouble is (for the fish), the seals find them anyway, even when the fish are sitting stock still.

Scientists were already aware that seals will track prey - even over long distances - by honing in on the currents fish make when they swim. But, according to the researchers, the new study answered a question that had bedeviled marine scientists: How do the seals find stationary, hiding fish?

For the study, the researchers used a special training tank, with a platform through which air currents – calibrated to simulate a flounder "breathing" - were pumped.

Then, trained seals from UR's marine science center were given eye masks and tested for their ability to locate the fake-flounder (in real life masters of hiding in plain sight) breathing. The seals did just that. With or without the blindfolds, the scientists found, they were able to locate the currents and move their snouts over the openings from which the currents were created – just as they would be able to locate the breathing of flounder camouflaged on the seafloor.

This seal has learned to wear an eye mask and headphones for behavioral studies.

When their whiskers were covered, though, as New Scientist noted, the seals weren't able to locate the currents.

It's all thanks to the whiskers. Study co-author Wolf Hanke has spent a fair amount of research time on them, discovering, in 2011 that seals can use them to "see" shapes echoed in water ripples, as Live Science reported.

Now, a new ability can be ascribed to them.

"Seals feel these water movements with their beard hair, even when the seal moves forward at velocities of one meter per second, and when further wind and wave currents are present," the scientists explained in a press release.